Monoculture Pasture Research Articles

222 Validation of Brix for predicting sugar concentration of alfalfa and orchardgrass

Abstract The objective of this study was to evaluate the accuracy of Brix in predicting sugar concentrations in fresh alfalfa (Medicago sativa L.; ALF) and orchardgrass (Dactylis glomerata L.; OG) forages to be used as an inexpensive and rapid field-level assessment of relative energy in forages. In a 2-yr study, fresh forages samples from ALF and OG monoculture pastures in central Pennsylvania, U.S. were collected once monthly from May to September. Samples were immediately evaluated for Brix values with a hand-held digital refractometer, and the remaining biomass was frozen immediately with liquid N to halt cellular respiration. Samples were lyophilized and analyzed for individual sugars and wet chemistry nutritive analyses. Brix values were correlated with wet chemistry analyses using the PROC CORR procedure in SAS, with significance established at P < 0.05. Brix was positively correlated (P < 0.05) with total and individual sugars in ALF during late spring and late summer (0.49 to 0.93), but correlations were non-existent (P > 0.05) or negative (-0.55 to -0.73; P < 0.05) in mid-summer. Brix values had moderate to strong negative correlations (P < 0.05) to NDF and ADF in ALF (-0.57 to -0.71). Conversely, Brix values did not correlate (P > 0.05) to any notable sugar parameters in OG beyond the first sampling date (0.60 to 0.74; P < 0.05). Brix was not correlated (P > 0.05) to NDF and ADF in OG. In summary, Brix values did not consistently predict sugar concentrations in fresh ALF and OG forages. Because Brix measures dissolved solids in solution (not just sugars), Brix readings collected from crushed ALF or OG samples may be confounded by fibrous fractions found in the solution as well as decreased sugar concentrations compared with fruit crops. Brix accuracy may also be dependent on seasonal temperature patterns, plant growth stage, and daily weather patterns. Other solutions should be investigated that rapidly assess sugar profiles and nutritive values of fresh forages.

Assessment of dry matter yield, nutritional value, and calf weight gain in Mombaza-Kudzu pasture associations.

O Objective: To evaluate the biomass production, nutritional value and animal production of an association with fabaceae species and grasses with grazing calves. Design/Methodology/Approach: The study compared Mombaza (Megathyrsus maximus) – Kudzu (Pueraria phaseoloides) association pasture against a Mombaza in monoculture control. Ten calves, five in each pasture type, were grazed in rotation for seven months. Dry matter yield, proportion of Kudzu in the association, protein, neutral detergent fiber (NDF), acid detergent fiber (ADF), ash, and daily weight gain were evaluated every 36 days. Results: Dry matter yield did not differ between pasture types, but varied by sampling dates, being higher at the onset of the rainy season (May 20th). The proportion of Kudzu in the association was low, decreasing from 8.42% to 1.71% over the study period. Lignin content increased in the association during the driest month (April). Daily weight gain was 978 g in the monoculture pasture and 678 g/day in the association, with no significant difference. Study Limitations/Implications: The low persistence of the fabaceae in the association limits the nutritional value of the pasture, consequently, the improvement of grazing animal production. Findings/Conclusions: During the drought season, both pastures exhibited the highest protein concentration and the greatest weight gain at the beginning of this period. However, the association did not result in greater weight gains due to the low persistence of the fabaceae.

Predicitng yield of irrigated red clover (Trifolium pratense L.) pastures in response to temperature.

Two datasets from red clover monoculture pastures grown in Lincoln, New Zealand, were analysed to generate coefficients to predict red clover yield. The mean annual production of established red clover was 17.0±0.48 t DM/ha, with a maximum mean growth rate of 125±9.36 kg DM/ha/day (spring Year 2). In the establishment year irrigated red clover grew at a constant rate of 7.30±0.14 kg DM/ha/°Cd (Tb = 3 °C) throughout the year. In contrast, there was a splitline linear response in Years 2 and 3, which differed between years and decreased after the second week of January. Specifically, the growth rate in Phase 1 was 7.70±0.38 kg DM/ha/°Cd in Year 2, which was 16% higher than the 6.60±0.28 kg DM/ha/oCd in Year 3. The difference probably reflected increased competition from weed grasses as red clover content declined from >95% to ~75% of total annual yield. After January, red clover grew at 3.05±0.35 kg DM/ha/°Cd, in both years. This lower rate occurred in the mid-January-July period, and probably reflected a change in partitioning of assimilate to red clover roots in response to a decreasing photoperiod. The coefficients reported here for red clover need to be validated from other datasets. However, they provide easily transferable coefficients that can be used to estimate red clover yield under nonlimiting conditions for other locations. These could be integrated into feed budgeting software to assist onfarm decision making.

Improving bermudagrass in the Southeastern United States with alfalfa as an alternative nitrogen source in grazing systems

AbstractBackgroundBermudagrass (Cynodon spp.) is one of the most common perennial warm‐season forages grown in the Southeastern United States. The incorporation of alfalfa (Medicago sativa) into bermudagrass pastures could serve as an alternative source of nitrogen (N) while also improving the nutritive value of the forage base.MethodsA 2‐year grazing evaluation arranged in a randomized complete block design was conducted from May to September 2018 (Year 1) and May–August 2019 (Year 2) in Tifton, GA, USA. The objective was to compare the production of alfalfa–bermudagrass mixed pastures (BGA) with bermudagrass monoculture pastures with (BGN) or without (BG) the application of synthetic nitrogen on forage production and stocker cattle performance.ResultsDifferences were observed for average daily gain (p = 0.10), gain per hectare (p = 0.02) and stocking rate (p = 0.01), in that BGA was greatest compared to BGN and BG, which did not differ from each other. Furthermore, BGA had increased forage crude protein (p = 0.01) and total digestible nutrients (p = 0.01) compared to BGN and BG. Finally, BGA provided the greatest economic return per hectare compared to BG or BGN.ConclusionsThese data illustrate improved animal performance and forage nutritive value using alfalfa–bermudagrass systems and offer a viable option for producers seeking alternatives to synthetic N sources for bermudagrass pastures in the Southeastern United States.

Nutritive value of Urochloa decumbens Stapf R. D. Webster and Mimosa caesalpiniifolia Benth. and performance of cattle in monoculture and silvopastoral systems, in the Agreste region of Pernambuco.

This study evaluated the nutritive value of signalgrass (Urochloa decumbens Stapf R. D. Webster) and sabiá (Mimosa caesalpiniifolia Benth.), and animal performance in grass monoculture pastures and in silvopastoral system (SPS) in the early development stage, in the Agreste of Pernambuco. Four treatments were evaluated in a randomized block design with three replications: signalgrass + Eucalyptus spp.; signalgrass + sabiá; signalgrass monoculture and sabiá monoculture. Holstein × Zebu crossbred calves (170 ± 15kg BW) were managed under continuous stocking with variable stocking rate (SR). The dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), and in vitro dry matter digestibility (IVDMD) of signalgrass and sabiá were assessed, as well as forage allowance (FA), stocking rate (SR), average daily weight gain (ADG) and weight gain per area (WGA) over eleven evaluation cycles (March 2019 to January 2020). Signalgrass had the highest DM contents in March 2019 and January 2020 (456 and 507gkg-1, respectively), while for IVDMD the highest values ranged from 436 to 547gkg-1 (April to August 2019). Sabiá presented the highest's IVDMD (311 and 381gkg-1 DM) and DM content (385 and 416gkg-1) and lowest CP (110 and 82gkg-1 DM) and NDF (568 and 500gkg-1 DM) in November 2019 and January 2020, respectively. FA and SR decreased throughout the evaluation cycles. ADG (0.38kg animal-1day-1) and WGA (17.89kgha-1 28days-1) did not differ among treatments, with weight loss in the period of low water availability. In the early development stage of the trees, SPS does not affect the nutritive value of signalgrass, nor the animal performance.

22 Incorporating Crabgrass in Southern Pasture Systems to Improve Animal Performance

Abstract Bahiagrass (Paspalum notatum L.) is a perennial warm-season forage commonly grown in the Coastal Plains of the Southeastern US, but the nutritive value may not be sufficient for a cow-calf pair. The inclusion of a warm-season annual, such as crabgrass (Digitaria sanguinalis) may improve the forage base when interseeded into bahiagrass monocultures. A three-year summer grazing evaluation was conducted at the University of Georgia Range Cattle Research Station in Alapaha, GA from 2019-2021 to compare concurring production of bahiagrass interseeded with an improved crabgrass (BCG) with bahiagrass monoculture (BG) pastures and animal performance. The experimental design was a randomized complete block with four replications. All paddocks were evaluated on a biweekly basis for herbage availability, botanical composition, and nutritive value. Paddocks (2.6 ha) were continuously grazed using the put-and-take method of stocking with cow-calf pairs, 4 tester pairs per treatment. Pairs were weighed at initiation and on a 28d interval for calculation of calf ADG, cow BCS, and gain/ha. Statistical analyses were conducted using the PROC MIXED procedure of SAS. Average daily gains were analyzed within year and treatment differences were only significant in Y1 (P = 0.05). Forage yield was never limiting in this experiment but CP and TDN were greater (P < 0.001) for BCG when compared to BG for Y1 and Y2. Rainfall was 27cm below average in Y1, therefore these data suggest that during a drought, crabgrass interseeded into bahiagrass can improve the forage nutritive value, and subsequent calf gain, as compared to bahiagrass alone.

Deep Soil Water Content and Forage Production in a Tropical Agroforestry System

Agroforestry systems integrating tree and forage growth are important for maintaining soil health but may change the soil’s physical-hydric properties. Our goal was to investigate the impact of introducing Eucalyptus trees into a pasture on the soil water content throughout the soil profile. The study was conducted in a 6-year-old agroforestry system where two species of Eucalyptus were introduced into a palisade grass pasture. Soil moisture was sampled at 0.0 (planting row), 2.0, 4.0, and 6.0 m (midpoint between tree rows) from the Eucalyptus tree rows. A monoculture palisade grass pasture was used as a control. The soil water content down to a depth of 50 cm was lowest in the tree row and increased with distance from the trees. In the Eucalyptus row, the soil water content in the 0–50 cm layer was lower than in the monoculture pasture. Agroforestry systems decreased the water content in the superficial layers of the soil in the rainy months; in the dry season, the soil water contents in all layers were similar between the Eucalyptus inter-rows. In most seasons, the agroforest systems reduced the forage production close to the Eucalyptus tree rows, up to 2 m from the trees, likely due to the soil water content decrease. Overall, this study showed that in tropical regions with sandy soils, the grass and trees’ competition must be considered when establishing integrated agroforestry systems in order to maximize the advantages and benefits of the diversified agroecosystem.

Tussock and tiller population dynamics on rotationally stocked Piatã palisadegrass (

Context Integrated crop–livestock–forestry systems can be an alternative to monoculture pastures; however, the effect of the arboreal component on tillering and tussock dynamics of understorey grass canopy is not well understood. Aims Our objective was to evaluate the patterns of tillering dynamics, population stability and tussock distribution of Piatã palisadegrass (Urochloa brizantha) as affected by contrasting shading regimes in the Brazilian Amazon biome. Methods The following three shading regimes were assessed: pasture with no trees (no shading, NS), moderate shading (MS, 338 trees ha−1), and intense shading (IS, 714 trees ha−1). Pastures were rotationally grazed by dairy heifers. Paddocks from MS and IS were stratified into three sampling strips, including two closer to the tree rows (i.e. lateral) and one between the two lateral strips (i.e. central). Two methods for monitoring sward canopy light interception (LI) were used for IS regime, namely, LI taken under the tree canopy (i.e. inside) and LI was taken above the tree canopy (i.e. outside). Key results Relative to NS, there was a reduction in photosynthetically active radiation transmittance of 18.1% and 37.1% on MS and 49.9% and 52.0% on IS for central and lateral shading strips respectively. Overall, the increase in shading level was associated with a decrease in average tussock perimeter, tiller population density, and an increase in the frequency of bare ground. Conclusions Our findings clearly indicate the key role of the light environment as a determinant of Piatã palisadegrass horizontal structure. Implications It highlights the importance of planning the levels of tree density and layout in areas of crop–livestock–forestry integration.

Proportion and digestibility of tree legumes in diets of grazing cattle in a tropical silvopastoral system

In Silvopastoral Systems (SPS) the dynamics and complexity of the combination between grasses and legume trees can significantly impact forage intake and digestibility, affecting livestock performance. This research was composed of two parallel studies. The first one consisted of a field trial assessing three grazing systems: signalgrass (Urochloa decumbens Stapf.) monoculture, and two SPS, one composed of signalgrass + gliricidia [Gliricidia sepium (Jacq.) Kunth.], and another by signalgrass + mimosa (Mimosa caesalpiniifolia Benth), in a randomized complete block design with three replications. Yearling crossbred 5/8 (Holstein/Zebu) steers (175 ± 29 kg initial body weight) were used as experimental animals. Response variables included δ13C in diet and the proportion of C3 species in the feces. The second study was an in situ dry matter digestibility (ISDMD) assay using fistulated male buffalos, and it was evaluated the increasing levels of each legume from the SPS (0, 25%, 50%, 75%, and 100%) in replacement to signalgrass, under different incubation period (24, 48, and 96 h). The range of the carbon isotope (δ13C) found in the cattle's feces (-14.2 to -16.4 ‰), in both signalgrass monoculture pastures and SPS, evidenced the preference of the cattle under SPS for consuming grasses (C4) instead of tree legumes (C3), as both were available. The carbon isotope (δ13C) in plants with C4 metabolism ranges between -9 and -16‰, and in C3 from -22 to -34‰. Increases in the intake of legumes during the dry period might have occurred due to lesser herbage mass and nutritive value of the grass. The ISDMD reached its greater values (>80%) in the inclusion levels of 75 and 100% of gliricidia, at 48- and 96-h incubation (P<0.05). Reductions in the ISDMD coefficients were observed increasing the levels of mimosa in the diet (P<0.01). Adding 100% of mimosa led to decreases in the ISDMD of 54.4% (24 h), 56.8% (48 h), and 49.1% (96 h). The species of legume tree can significantly affect the preference, proportion of C3/C4 species, and the digestibility of the diet of grazing animals in SPS. The grazing cattle in SPS showed a preference for consuming grass instead of legume trees, however, gliricidia was preferred compared to mimosa, especially in periods of lesser grass availability.

Changing ecological and agricultural expectations for US Coastal Plain managed grasslands

Across the US Coastal Plain, native grasses and legumes may provide viable alternatives to monoculture pastures of introduced sod‐forming grasses, which require recurring costly inputs. Some available cultivars of native grasses, mostly from neighboring regions, have potential to combine forage production for grazing livestock with enhanced habitat, especially for grassland birds. A few native legume species have potential to enhance ecosystem service provisioning of existing grass pastures. Such pastures with native grasses and legumes could complement restoration plantings to increase connectivity and scale of ecosystem function; however, coordination of pasture and restoration plantings would be needed to optimize benefits.

Health-Promoting Phytonutrients Are Higher in Grass-Fed Meat and Milk

While commission reports and nutritional guidelines raise concerns about the effects of consuming red meat on human health, the impacts of how livestock are raised and finished on consumer health are generally ignored. Meat and milk, irrespective of rearing practices, provide many essential nutrients including bioavailable protein, zinc, iron, selenium, calcium, and/or B12. Emerging data indicate that when livestock are eating a diverse array of plants on pasture, additional health-promoting phytonutrients—terpenoids, phenols, carotenoids, and anti-oxidants—become concentrated in their meat and milk. Several phytochemicals found in grass-fed meat and milk are in quantities comparable to those found in plant foods known to have anti-inflammatory, anti-carcinogenic, and cardioprotective effects. As meat and milk are often not considered as sources of phytochemicals, their presence has remained largely underappreciated in discussions of nutritional differences between feedlot-fed (grain-fed) and pasture-finished (grass-fed) meat and dairy, which have predominantly centered around the ω-3 fatty acids and conjugated linoleic acid. Grazing livestock on plant-species diverse pastures concentrates a wider variety and higher amounts of phytochemicals in meat and milk compared to grazing monoculture pastures, while phytochemicals are further reduced or absent in meat and milk of grain-fed animals. The co-evolution of plants and herbivores has led to plants/crops being more productive when grazed in accordance with agroecological principles. The increased phytochemical richness of productive vegetation has potential to improve the health of animals and upscale these nutrients to also benefit human health. Several studies have found increased anti-oxidant activity in meat and milk of grass-fed vs. grain-fed animals. Only a handful of studies have investigated the effects of grass-fed meat and dairy consumption on human health and show potential for anti-inflammatory effects and improved lipoprotein profiles. However, current knowledge does not allow for direct linking of livestock production practices to human health. Future research should systematically assess linkages between the phytochemical richness of livestock diets, the nutrient density of animal foods, and subsequent effects on human metabolic health. This is important given current societal concerns about red meat consumption and human health. Addressing this research gap will require greater collaborative efforts from the fields of agriculture and medicine.

Seasonal greenhouse gases fluxes from monoculture and mixed native grasslands in the Southern Plains, USA

AbstractAgricultural practices have been linked to soil carbon (C) and nitrogen (N) stores through exchanges with the atmosphere in the form of greenhouse gases (GHGs) of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). However, regional and management‐specific research is needed to ultimately understand the drivers of these atmosphere warming molecules. We established research on four grassland sites: a native, mixed‐species warm‐season site and a non‐native, warm‐season, grass‐species site at the Grazinglands Research Laboratory at El Reno, OK; a native, mixed‐species warm‐season site at Noble Research Institute's Oswalt Ranch in Ardmore, OK; and a native, mixed‐species, warm‐season site at Oklahoma State University's Range Research Station at Marena, OK. Greenhouse gases, along with soil properties were measured biweekly and summed by season in 2015 and 2016. A comparison of GHGs with soil variables indicated that mineralization of soil nutrients mediated GHG fluxes. The sites were sources of CO2 and N2O emissions, but sinks for CH4, particularly in diverse native grassland sites. In spring, CO2 emissions were driven by soil water content, soil temperature, and soil N. The N2O emissions were highest in the fertilized monoculture pasture. Overall, fluxes of the GHGs were driven by primarily by water content, soil nitrate, soil temperature, and ammonia content. By better understanding GHG fluxes and the abiotic and biotic drivers, we can identify management options to foster C sequestration and mitigate the GHG footprint for these forage‐based systems.

76 Evaluating Nitrogen Management Strategies to Improve Southern Bermudagrass Grazing Systems

Abstract Bermudagrass (Cynodon dactylon) is one of the most common perennial warm-season forage crops grown in the South. While prominent in the region bermudagrass management requires large amounts of fertility and forage quality is moderate at best. Incorporating a legume into bermudagrass pastures could serve as an alternative to the necessary applications of synthetic N, while also improving the nutritive value of the forage base. A two-year grazing evaluation was conducted from May-Sept. 2018 (Y1) and May-Aug. 2019 (Y2) at the University of Georgia Tifton Campus in Tifton, Georgia, to compare concurring production of alfalfa/bermudagrass mixed pastures (BGA) with bermudagrass monoculture pastures with (BGN) or without (BGZ) the application of synthetic nitrogen. The experimental design was a randomized complete block with three treatments and two replications. All paddocks were evaluated pre and post grazing event for herbage availability, botanical composition, forage species competitiveness, and nutritive value. Paddocks (0.8-ha) were rotationally grazed using put and take management with stocker steers (Y1 BW=195.9±22.9 kg; Y2 BW=228.5±30.0 kg), two testers per treatment. Steers were weighed at initiation, conclusion, and on a 28–30 day interval for calculation of ADG and gain/ha. Statistical analysis was conducted using the PROC MIXED procedure of SAS. Despite significant drought in Y2, year did not affect total gain/ha, however treatment did (P = 0.04), such that BGA was highest (383.6±35.1 kg/ha), and BGN and BGZ were not different (261.2±35.1 kg/ha and 239.0±35.1 kg/ha, respectively). This is likely due to the lower stocking density and inclusion of high-quality volunteer annual grasses in BGZ treatments which allowed for selective grazing. These data suggest that rotationally grazing alfalfa/bermudagrass mixtures can result in a higher gain/ha, than bermudagrass pastures that are supplemented with or without synthetic N in the South.

77 Evaluating Nitrogen Management Strategies to Improve Southern Bermudagrass Grazing Systems

Abstract Bermudagrass (Cynodon dactylon) is one of the most common perennial warm-season forage crops grown in the South. While prominent in the region bermudagrass management requires large amounts of fertility and forage quality is moderate at best. Incorporating a legume into bermudagrass pastures could serve as an alternative to the necessary applications of synthetic N, while also improving the nutritive value of the forage base. A two-year grazing evaluation was conducted from May-Sept. 2018 (Y1) and May-Aug. 2019 (Y2) at the University of Georgia Tifton Campus in Tifton, Georgia, to compare concurring production of alfalfa/bermudagrass mixed pastures (BGA) with bermudagrass monoculture pastures with (BGN) or without (BGZ) the application of synthetic nitrogen. The experimental design was a randomized complete block with three treatments and two replications. All paddocks were evaluated pre and post grazing event for herbage availability, botanical composition, forage species competitiveness, and nutritive value. Paddocks (0.8-ha) were rotationally grazed using put and take management with stocker steers (Y1 BW=195.9±22.9 kg; Y2 BW=228.5±30.0 kg), two testers per treatment. Steers were weighed at initiation, conclusion, and on a 28–30 day interval for calculation of ADG and gain/ha. Statistical analysis was conducted using the PROC MIXED procedure of SAS. Despite significant drought in Y2, year did not affect total gain/ha; however, treatment did (P = 0.04), such that BGA was highest (383.6±35.1 kg/ha), and BGN and BGZ were not different (261.2±35.1 kg/ha and 239.0±35.1 kg/ha, respectively). This is likely due to the lower stocking density and inclusion of high-quality volunteer annual grasses in BGZ treatments which allowed for selective grazing. These data suggest that rotationally grazing alfalfa/bermudagrass mixtures can result in a higher gain/ha, than bermudagrass pastures that are supplemented with or without synthetic N in the South.

Silvopastoral system for resilience of key soil health indicators in semi-arid environment

ABSTRACT Poor land utilization is always a concern in semi-arid regions. This study was conducted to examine the effect of different silvopastoral systems on soil chemical, biological and biochemical properties after 9 years of establishment. All studied soil properties were influenced by different land use systems except soil pH. Guava + pasture system recorded higher organic carbon [OC ~12 Mg ha–1], N (~257 kg ha–1), fungi (~43 × 107 cfu g−1 soil), alkaline (35.83 µg p-nitrophenyl g–1 soil h–1), and acid phosphatase (32.84 µg p-nitrophenyl g–1 soil h–1) activities compared to other land use systems. Whereas, microbial biomass carbon [MBC, ~92 mg kg–1 soil] content and total bacteria (239 × 107 cfu g−1 soil) counts were higher under bael + pasture system. Increased soil pH (7.1 to 7.4) in the monoculture pasture system favored the P content (~35 kg ha–1) over other land use systems. All the soil properties were higher in 0–15 cm compared to 15–30 cm depth. Our results demonstrate that for the resilience of key soil health indicators, the long-term guava + pasture and bael + pasture systems can be a promising option for semi-arid environment.

Soil microbial community, enzyme activity, C and N stocks and soil aggregation as affected by land use and soil depth in a tropical climate region of Brazil.

The impact of agricultural land-use on soil microbial community composition and enzyme activity has not been extensively investigated in Ultisols. We investigated soil health parameters by analyzing phospholipid fatty acids (PLFAs), extracellular enzyme activity, C and N stocks, and soil structure. Four land uses were established in a tropical climate region of Brazil: native Cerrado (savanna), monoculture pasture [Urochloa brizantha (Hochst. Ex A. Rich.) R. Webster 'Marandu'], an integrated crop-livestock system (ICLS), and maize (Zea mays)-fallow in a no-tillage system. Soil microbial biomass was 40% higher in the native Cerrado than in the monoculture pasture, ICLS, and no-tillage maize. Soil organic carbon was positively correlated with microbial community composition (MB; gram-; AC; AMF; Fungi; F: B ratio) and enzyme activity (bG, AP, NAG). Large macroaggregates were positively correlated with bG, AP, and AMF. In summary, the native Cerrado had a higher level of carbon at the soil surface and greater soil structure with increased microbial biomass, gram+ bacteria, AMF, fungi, and F:B ratio in a tropical region of Brazil. However, bG and AP enzyme activities were lower in the ICLS and no-till maize at the soil surface (0-5cm) compared to the native Cerrado. The conversion of native Cerrado to agricultural systems shifted the soil microbial community composition, enzyme activity, C and N, and soil structure of this sandy soil of the Brazilian Cerrado.

In vitro digestibility of mountain-grown irrigated perennial legume, grass and forb forages is influenced by elevated non-fibrous carbohydrates and plant secondary compounds.

Perennial legumes cultivated under irrigation in the Mountain West USA have non-fibrous carbohydrate (NFC) concentrations exceeding 400 g kg-1 , a level commonly found in concentrate-based ruminant diets. Our objective was to determine the influence of NFC concentration and plant secondary compounds on in vitro rumen digestion of grass, legume and forb forages compared with digestion of their isolated neutral detergent fiber (NDF) fraction. Forages were composited from ungrazed paddocks of rotationally stocked, irrigated monoculture pastures between May and August 2016, frozen in the field, freeze-dried, and ground. The maximum rate (RMax ) of gas production was greater for the legumes alfalfa (ALF; Medicago sativa L.) and birdsfoot trefoil (BFT; Lotus corniculatus L.) than for the legume cicer milkvetch (CMV; Astragalus cicer L.) the grass meadow brome (MBG; Bromus riparius Rehm.) and the non-legume forb small burnet (SMB; Sanguisorba minor Scop.), and intermediate for the legume sainfoin (SNF; Onobrychis viciifolia Scop.). The RMax of isolated NDF was greatest for BFT and CMV, intermediate for ALF, SNF and SMB and least for MBG. More than 900 g of organic matter kg-1 dry matter of legumes was digested after 96 h. Across forages, the extent of whole-plant digestion increased with NFC and crude protein concentrations, decreased with NDF concentrations, and was modulated by secondary compounds. The extent of digestion of isolated NDF decreased with concentration of lignin and residual tannins. © 2020 Society of Chemical Industry.

Deep soil carbon stock, origin, and root interaction in a tropical integrated crop–livestock system

Integrated crop–livestock systems (ICLS) with fast-growing tree plantations are an environmentally sound approach for agricultural production. Soil carbon stocks can be increased under these systems, but there is no information on the relative contributions of the pasture and the trees in building soil C in tropical regions. This study aimed to investigate C storage, origin, and roots sequestration in the soil profile (1.0 m) in a pasture-forest system. The study was conducted in a 6-year-old ICLS in which Eucalyptus (C3) were introduced into a palisade grass pasture [Urochloa brizantha (Hochst. Ex A. Rich.) R. Webster ‘Marandu’, C4]. Samples were collected at four locations perpendicular to the Eucalyptus planting line: 0 (planting line), 2.0, 4.0, and 6.0 m (middle of the plot). A monoculture palisade grass pasture was included for comparison. The insertion of Eucalyptus in the pasture modified the quantity and distribution of grass above and belowground. Forage root and shoot biomass were lower in the integrated system compared to the monoculture pasture, mainly near Eucalyptus. However, plant C sequestration in the ICLS was 68% higher than in the monoculture pasture, due to the C accumulated by aboveground trees biomass. Overall, monoculture pasture had higher soil C4–C stocks at the 0–0.20 m depth, while integrated system with Eucalyptus stored more C3–C in deeper soil layers (0.60–1.0 m) near Eucalyptus. Soil C stock increased in both systems, but the contribution of Eucalyptus was deeper in the soil profile, while the grass contribution was greater in the upper 0.20 m soil layers.

Root and shoot interactions in a tropical integrated crop–livestock–forest system

Integrated crop–livestock–forest systems (ICLFS) have potential advantages compared to monoculture, but most studies quantifying plant biomass in integrated production systems, have quantified only the aboveground component rather than the total biomass. The objective of this study was to investigate the ecological interactions of Eucalyptus trees intercropped with palisade grass in a tropical region. The study was conducted in an 8-year-old ICLFS in which Eucalyptus trees were introduced into a palisade grass pasture [Urochloa brizantha (Hochst. Ex A. Rich.) R. Webster ‘Marandu’]. Samples were collected at four locations from the Eucalyptus trees: 0.0 (planting line), 2.0, 4.0, and 6.0 m (middle of the plots). A monoculture palisade grass pasture was included for comparison. The addition of Eucalyptus in the pasture reduced the forage yield, root length density, root density and root diameter of palisade grass close to the Eucalyptus trees. Eucalyptus roots were more abundant near the trees, and decreased with distance from the tree at soil depths up to 1.0 m. The total amount of roots decreased by 36 % with the addition of the forest component compared with the monoculture pasture, i.e., 11.6 Mg ha−1 in the ICLFS compared with 18.4 Mg ha−1 in the pasture. In the ICLFS, the proportion of palisade grass roots in the soil profile increased with distance from the tree line. However, the high degree of competition in root development in the ICLFS resulted in 20% lower root length and fine roots densities compared with monoculture pasture in the upper 0–0.20 m soil layer.

Microclimate effects on canopy characteristics of shaded palisadegrass pastures in a silvopastoral system in the Amazon biome of central Brazil

Abstract Forage grass canopies may be affected by the shaded microclimate in silvopastoral (SP) systems throughout the year. This in turn may affect forage plant characteristics. Our objective was to assess microclimate effects on the responses of Marandu palisadegrass {Urochloa brizantha (Hochst. ex A. Rich.) R. D. Webster [syn. Brachiaria brizantha (Hochst. ex A. Rich.) Stapf.]} under continuous stocking in an SP system with Eucalyptus urograndis (hybrid of Eucalyptus grandis W. Hill ex Maiden and Eucalyptus urophylla S. T. Blake). Trees were planted in triple rows (grove), with three groves per 2-ha silvopasture experimental unit (11° 51′ S, 55° 35′ W). The spacing between groves was 30 m, and tree density was 135 ha–1, in East-West orientation. Microclimate and forage plant variables were evaluated from December 2016 to March 2018 in the treatments consisting of “full sun” (FS) grass monoculture pasture and at three distances from the grove: 7.5 m North (7.5 N), 15 m (15), and 7.5 m South (7.5S). Photosynthetically active radiation (PAR) was greatly affected and positively associated with most of the responses of Marandu palisadegrass. On average, PAR reduction in relation to FS was 8, 24, and 40 % for 15, 7.5 N, and 7.5S, respectively. The greatest maximum temperatures (35.8 °C) and the least minimum temperatures (15.8 °C) were registered during the Winter. Both forage accumulation rate (∼ 45 kg ha−1 d-1) and leaf accumulation rate (∼ 19 kg ha-1 d-1) were similar between FS and 7.5S (most shaded distance). Shade tolerance mechanisms of palisadegrass under grazing were associated with increases in specific leaf area and leaf proportion, allowing shaded pastures to sustain productivity at levels equivalent to those of pastures without shade.